This proposal is submitted as part of the application for a Research Career Award for Domenica G. Sweier, D.D.S. A Research Career Award will enable the applicant to complete her graduate dentist scientist training in the Oral Health Sciences Ph.D. Program at the University of Michigan School of Dentistry. The objective of this proposal is to investigate the role of the P. gingivalis Hsp90 homologue in the pathogenesis of the microorganism in periodontal disease. Heat shock proteins have been found to be important in many soft tissue infections and have been referred to as virulence factors in some models. For example, the overexpression of Saccharomyces cerevisiae Hsp90 enhances the virulence of this organism in mice (Hodgetts et al., 1996). In humans, anti-Hsp90 seroconversion is associated with a higher survival rate in systemic candidiasis. Moreover, in candidiasis, antibodies to a specific conserved epitope were shown to confer protection (Matthews et al., 1995). Heat shock proteins have also been implicated in adherence mechanisms. A 66kDa Hsp of Salmonella typhimurium is believed to be responsible for binding to the intestinal mucosa and is considered a virulence factor in this microorganism (Ensgraber and Loos, 1992). Elevated levels of serum antibodies to purified human Hsp90 in healthy adults were associated with periodontal health (manuscript in preparation). Healthy individuals had higher anti-Hsp90 serum antibodies than those individuals diagnosed with periodontal disease. Additionally, the P. gingivalis Hsp90 homologue has been found to cross-react with anti-human Hsp90 stress protein antibodies. We feel that further studies on the role of the Hsp90 homologue of P. gingivalis in host-bacteria interactions in periodontal disease will result in the development of new diagnostic and therapeutic modalities. The studies proposed in this application will address the following global hypothesis: Specific epitopes of the Porphyromonas gingivalis Hsp90 homologue are putative virulence determinants that may be blocked by antibodies in sera of healthy subjects. In order to begin to address this hypothesis, we proposed to: (1) clone and characterize the P. gingivalis hsp90 gene homologue, (2) express the P. gingivalis hsp90 gene homologue and harvest the protein, and (3) map the immunodominant epitopes recognized in health and disease.